Many agricultural and industrial prime movers are equipped with auxiliary implement drive systems which are powered by mechanically driven power take-offs or directly connected hydraulic power. A non-limiting list of typical implements includes rotary and flail mowers, snow blowers, rotary tillers, landscape preparators, trenchers, etc. Typically implements have a required horsepower rating based on power take off speeds of either 540 or 1000 rpm. Optimal operation of these implement systems requires a sufficient amount of horsepower at the rated speed being transmitted to the implement combined with a suitable ground speed and resulting feed rate. The ground speed and resulting feed rate to the implement depend on transmission and gear/speed selection. With the current conventional drive systems, an ideal or optimal application would have the prime mover (for example a tractor, back-hoe, bulldozer, or skid/steer loader) operated at a constant engine speed so as to optimize the implement input horsepower. In very few circumstances is this ideal possible.
In most combinations, the horsepower supplied to the implement is directly related to the prime mover's engine speed. Typical transmissions and gears are in fixed proportions. Therefore when the engine speed slows, so does the supplied horsepower and speed of the implement. A sufficiently slow ground speed can result in a reduction in supplied horsepower below the implement's rating, resulting in a drop in the implement's efficiency.
Prime movers with mechanical or conventional hydrostatic power take off or hydrostatic/hydraulic drive system have some functional disadvantages:
One common disadvantage of conventional power take-offs, either mechanical or hydraulic, is that the auxiliary implement speed and relating drive horsepower are directly proportional to the prime mover engine speed. As an example, when the vehicle/engine speed is slowed for improved and safe maneuverability, the auxiliary implement loses operating efficiency and inertia, resulting in poorer performance and overloading the prime mover engine. Currently this must be overcome by methods such as disengaging the ground drive and speeding up the engine, selecting a low ground speed (gear), or reducing the load on the implement. For a mower or flail, a reduced load is typically done by raising the implement's height, resulting in less output and/or requiring multiple applications of the implement.
Another typical disadvantage of conventional power take-offs is that if a reduction in feed rate to the implement is required due to heavier than normal conditions, the operator must make a ground speed reduction via the vehicle transmission (gear change) due to the fact a simple ground speed reduction via engine speed results in a proportional drop off in power to the implement thus potentially overloading the prime mover engine.
Certain embodiments of the present invention address these and other needs.